Conventionally, there is provided a head-up display apparatus for displaying images related to a subject vehicle and an obstacle such as a pedestrian or a different vehicle detected around the subject vehicle. For example, the head-up display apparatus described in patent literature 1 displays relative positional relation between a subject vehicle image and an obstacle image and thereby allows an occupant to recognize where an obstacle actually exists around the subject vehicle. The head-up display apparatus displays the subject vehicle image representing the whole of the subject vehicle and thereby allows the occupant to recognize a front, back, right, or left direction of the subject vehicle image. The head-up display apparatus also displays the relative positional relation between the subject vehicle image and the obstacle image. The occupant can thereby recognize an actual obstacle position relative to the subject vehicle.